diff --git a/composer.json b/composer.json
index 57a5c02..474ddee 100644
--- a/composer.json
+++ b/composer.json
@@ -19,14 +19,15 @@
     },
     "require":{
         "php":">=5.4",
-        "contao/core":">=3.2,<3.6-dev"
+        "contao/core":"~3.5"
     },
     "suggest": {
         "netzmacht/contao-leaflet-maps": "Leaflet maps integration into Contao CMS"
     },
     "extra":{
         "branch-alias": {
-            "dev-master": "0.7.3.x-dev"
+            "dev-master": "0.7.3.x-dev",
+            "dev-leaflet-v1": "1.0.x-dev"
         },
         "contao": {
             "sources":{